I had set the tasks java options at -Xmx1.5g, that needed to be -Xmx1500m,the telltale output of a mistake like that is rather tricky to find, I hadto dig into the task tracker UI/logs, it doesn't show up on the jobtracker's normal logs.

The timing perfectly coincided with a DNS change, and Googles first hit, onthe error that I *could* see in the jobtracker logs, suggested DNS, so Iwent down that rabbit hole for quite a while.